Myoelectric prostheses were reported to be practical and effective by Hermansson et al. based on their myoelectric prosthesis usage survey of myoelectric prosthesis users (n=75) [1] . Moreover, there are reports affirming that myoelectric prostheses play an important role in achieving rehabilitation goals [2] [3] [4] . However, this previous research involved survey-based retrospective studies. Therefore, while these studies support the usefulness of myoelectric prostheses, their findings are

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... t based on firm scientific evidence [1] . Furthermore, Resnik reported that the effects of myoelectric prosthesis training on the ability of amputees to operate upper limb prostheses are unclear [5] . Hence, it is necessary to clarify the effects of myoelectric hand operation training based on objective data. Myoelectric prosthesis operation training was proposed by Atkins in 1992 [6], and associated guidance was formulated by Johnson et al. in 2015 [7]. The training was organized into single-handed and dual-handed tasks, and it was recommended that dual-handed tasks should be performed after practicing single-handed tasks [6, 7] . However, there are no objective data to verify how single-handed and dual-handed tasks affect amputees' ability to operate myoelectric prostheses. The